The Walvis Basin and indeed Block 2113A is a key potential oil and gas frontier area and forms a greater part of the unexplored sector of the Namibian continental margins located south of the prolific Angolan mature oil fields. This major Cretaceous-Recent depositional geological system covers an area of over 105,000 km2, and has a wedge-shaped geometry typical of passive margin post-rift sequences. Petroleum Exploration License (PEL) 58, Block 2113A, offshore Erongo Province, Namibia covers 5,750 km2, with 3,600 km2 located offshore and 2,150 km2 located onshore. PEL 58 is located inboard of Pancontinental‟s PEL 37 Block and adjacent to EcoAtlantic‟s CBM Blocks 2013B, 2014B & 2114. On the 20th March 2015, Nabirm concluded a 2D seismic survey which included the acquisition of gravity and magnetics data; the campaign was contracted to BGP International.
BGP acquired the Data using the 3D vessel M/V BGP Pioneer just off a similar 2D campaign for ION Geophysical offshore Namibia.The project scope consisted of a FIRM 684 full fold km of 2D marine seismic acquisition including renewed gravity and magnetics. The survey was acquired by BGP International using the vessel M/V BGP Pioneer; earlier in 2015 the same vessel completed the Ion Geophysical NamibiaSPAN 2D survey in offshore. The Nabirm 2D seismic survey is located in the southwest portion of Block 2112A, PEL 58 and encompasses approximately a 2275 kilometers2 (km2) area
The survey consist of 24 lines including 5 strike lines (oriented parallel to the Namibia coast) and 19 dip lines (oriented perpendicular to the Namibia coast). The longest strike line (Line 1) is 80 kilometers (km) in length; the longest dip line (Line 34) is 40 km in length. The survey area extends from 18 km to 57 km offshore. The 2D seismic grid spacing is 3 km x 4 km with the exception of strike Line 9, which is 7.5 km from strike Line 7. Odd numbered Lines 1, 3, 5, 7 and 9 are oriented parallel to the coastline (strike lines) with Line 1 occurring adjacent to the coast; Line numbers increase moving basinward.
Even numbered Lines 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36 and 38 are oriented perpendicular to the coastline (dip lines) with Line 2 positioned at the North end of the survey and Line 38 at the South.
The 2D seismic data were processed by Parallel Geoscience in April and May of 2015. Ion Geophysical was contracted to perform the 2D seismic interpretation and received/loaded the processed 2D dataset into SMT/Kingdom on 6 July, 2015. Two Ion Geophysical NamibiaSPAN 2D seismic lines are located near the Nabirm 2D seismic survey area. These lines are NAM-3500, located 33 km northwest and NAM-4000, located 6 km southeast. The nearest well to the Nabirm 2D seismic survey is the Ranger Oil 2213 6-1 well located 33 km southwest of the survey area. The 2213 6-1 well is located on NamibiaSPAN line NAM-4000.
In November 2015 ION completed the interpretative study for Nabirm integrating its regional data into the project. The objective of the seismic interpretation was to identify key depositional features (reflection types, continuity, terminations, downlap, top lap, onlap), structural features (highs, lows, faults and fault stylesincludingnormal,reverse,strike-slip)andanomalousreflectionpackages. Keyhorizonswere selected based on reflection strength, continuity and their relative position to genetically related successions of sediments.
Time structure maps, depth structure maps, isochrons and isopachs were generated for key horizons including Surface 1, Surface 2, Surface 3 and basement. Utilizing the correlation of well 2213 6-1 with NamibiaSPAN horizons, Surface 1 approximately correlates to top Cretaceous. Surface 2 and Surface 3 are of unknown age, yet based on the NamibiaSPAN horizon interpretation the horizons maybe Campanian, Santonian or Coniacian age. Karoo age sediments may occur below Surface 3 or may occur as a thin veneer adjacent to basement throughout the survey area. Time structure maps, isochrons, depth structure maps and isopachs were created for the Block 2113A 2D survey area. Additional isopach maps were created to identify possible stratigraphic traps above basement.
ION mapped six leads with total Pmean unrisked recoverable resources of over 520 MMBO. Stratigraphic lead 5 is the largest and of principal interest, with a Pmean of around 230 MMBO. Lead 6 is slightly smaller and exceeds 200 MMBO. In 2014, Pancontinental Oil & Gas, in partnership with Tullow Oil Plc have mapped an “Oil Mature Fairway” through EL 0037 and the HRT Wingat-1 well area. Critically, using existing seismic data, good reservoir rocks are interpreted in channels and turbidites within and close to the Oil Mature Fairway in EL 0037.
DeGolyer and MacNaughton (“D&M”) prepared an assessment of licence area PEL 37 offshore Namibia in accordance with the Petroleum Resources Management System (PRMS) approved by the Society of Petroleum Engineers, the World Petroleum Council, the American Association of Petroleum Geologists, and the Society of Petroleum Evaluation Engineers. D&M’s resource estimates recognize large stratigraphic leads in potential clastic turbidite targets. These targets appear to be in the oil window. These potential accumulations are categorized as “leads” based on the available seismic and geologic data. The potential accumulations are not yet classified as “prospects” that are available for drilling. D&M’s Mean Estimate for the total 11 Leads is 8.7 Billion Barrels of Gross Prospective (recoverable) Oil Resources.
PEL 0037 is adjacent to NABIRM’s acreage PEL 0058, Block 2113A.
Offshore Namibia is an oil-prone area with multiple recognized marine and lacustrine source rocks. The stacked distribution of source intervals enhances probability of a working petroleum system. Numerous occurrences of marine and lacustrine-derived petroleum have been documented in the offshore basins of Namibia and South Africa.Gas occurrences are generally the result of high levels of maturity of marine & lacustrine sources due to deep burial, high heat flow and high geothermal gradients.
Source rock type, richness, distribution and level of maturity are favorable for the generation and expulsion of significant volumes of oil. Basins in offshore Namibia are similar to other passive-margin basins in the South Atlantic including Brazil, Angola, Gabon, Congo, Equatorial Guinea, Uruguay and Argentina. Three petroleum source intervals have been identified from offshore wells and DSDP/ ODP sites. The three source intervals are rift (lacustrine), Lower Cretaceous Barremian-Aptian (marine) and Cenomanian-Turonian (marine) sources. Pre-rift (Karoo) source intervals are likely present and may generate gas, yet the offshore data is inadequate to assess their contribution.
ION’s interpretation of Nabirm’s data; the established oil kitchen in the Walvis Basin confirming light 40 API degrees gravity oil; the oil shows onshore on Eco Atlantic’s Daniel Block which prompted the drilling of the Toscanini Well; and the slicks evident in the region from the Fugro Oil Slick study that was completed for Eco Atlantic, all indicate that Exploration in blocks adjacent to PEL 58 identify an oil mature fairway. Hydrocarbons generated within this fairway would be migrating eastward and updip toward Block 2113A. In onshore blocks, exploration is focused on Karoo age sediments. There is a high likelihood of Karoo sediments in Block 2113A. The Lower Cretaceous Twyfelfontein Sandstone has been mapped extensively onshore and likely extends into the offshore area. The Twyfelfontein Formation – Verbrande/Tsarabis/Huab Formations would be key reservoir-source rock components of a viable Petroleum System within Block 2113A. Offshore Namibia is an oil-prone area with multiple recognized marine and lacustrine source rocks.